Means of feeding alternating current arcs



Dec. 12, 1933. BETHENQD' 7 1,938,618

MEANS OF FEEDING ALTERNATING CURRENT ARCS Filed Jan. 27, 1931//W[/V/'0/\. J A Bel/5806a? B) i W HT/VZ/FA/[Y Patented Dec. 12, 1933UNITED STATES PATENT OFFICE MEANS OF FEEDING ALTERNATING CURRENT ARCSJoseph Bethenod, Paris, France, assignor to Radio Patents Corporation,New York, N. Y., a corporation of New York Application January 27, 1931,Serial No. 511,491,

and

2 Claims.

amperes must be taken much greater than the watts consumed by the are,if unity power factor is required.

According to the second method, the condenser is connected in parallelwith the welding are itself, and the working conditions of the condenserare quite different, It can be shown that it is then possible to obtainunity power factor with a capacitance, the volt amperes of which areonly equal to the watts consumed by the arc.

However, the latter method presents some difficulties, chiefly about thestriking of the arc, when the electrodes are cold. Oscillatorydischarges take place then between the said electrodes, and very stronghigh frequency currents can be induced in some parts of the plantSimilar phenomena occur when the working conditions of the are aredisturbedf in any way.

According to the presentiinvention, means are provided to preventsuchoscillato fy discharges, the effect of which can ,befyery'del'e'terious.The accompanying drawing illustrates,- by [.way of examples, twoembodiments'of ,the*invention:

Figure 1 is a circuit diagram. according which the are 1 is fed bymeans'of a'transformer-E, 3, the primary of which '2, iszconnebted,alternating current supply .8 through termediary 1015 an ironorejurductance; coil 4, I which ensures the requireddroqpin'g volt+ampere 40characteristic ofthe feeding circuit. The capacitor '7 is inparallel-relation'with the-said arc, "and when the electrodes are cold,very strong discharges of very high frequency occur, owing to the verylow impedance of the discharge circuit. In order to prevent suchdischarges, an inductance 5 is placed in series with the capacitor 7, soas to reduce the frequency of the discharges; on the other hand, aresistor 6 can be added in the purpose of increasing the damping of thesaid discharges. It is thus possible to limit to the desired extent theeffect of the induced electric surgings, without interfering with theefllciency of the plant. According to the diagram of Fig. 2, the sameresult can be ob- 55 tained without any additional impedance, if the inFrance January 30, 1930 capacitor 7 is connected to a tertiary winding 9of the feeding transformer. When the permanent state is reached, theeffect of the capacitor is then equivalent to the effect of a capacitorshunting the arc, but when transient phenomena to occur, no highfrequency discharges of the said capacitor can take place between theelectrodes, owing to the internal impedance of the transformer. Ofcourse; the said tertiary winding can be combined with one of thewindings 2 and 3,

so as to form an auto-transformer; furthermore,

in some cases, the capacitor can be connected directly to the terminalsof the primary winding 2.

Finally, it should be noticed that it is possible to'reduce the powerdelivered to the are by increasing the inductance 1 of the coil 4; if,at the same time, the capacity 0 of the capacitor '1 is diminished, sothat the product 1 0 remains nearly constant, unity power factor isavailable, whatever be the load.

I wish it to be understood that I do not desire to limit myself to thearrangements herein set forth, as it is obvious that variousmodifications may be made therein without departing from the essentialfeatures of my invention as defined in the appended claims:

I claim:

1. In an electrical system, a source of alterhating current; an arc gapelectrically connected to said source of alternating current; acapacitor electrically connected to said source of alternating currentin parallel with said are gap; and an inductance coil electricallyinterposed between said source of alternating current and said cavpacitor and arc.

2. In an electrical system, a source of power supply; an arc gapelectrically connected to said source of power supply; a capacitor elec-JQSEPH BETHENOD.

